The Federal Communications Commission (FCC) has adopted certain architectural standards with respect to electrical connectors utilized in the telecommunication industry so as to provide intermatability. The connectors most commonly utilized are FCC type modular plugs and jacks, also referred to as RJ-45 plugs and jacks. The plug is commonly terminated to a plurality of conductors which may be connected to a communication device. Normally, each plug is terminated to eight conductors which form four pairs. The corresponding jack is commonly mounted to a panel or a printed circuit board (PCB) or a wall outlet, which in turn is connected to the telecommunication network. To complete the circuit, the plug and jack are intermated.
In RJ-45 telecommunication jack design, it is necessary to have a compensating structure that overcomes the noise generated within the plug. The noise is generated due to the coupling between the conductors, known as crosstalk, based on the mutual capacitive and mutual inductive interferences between signal lines. Accordingly, crosstalk can be classified into capacitive crosstalk and inductive crosstalk. As explained in the U.S. Pat. No. 5,299,956, which was assigned to Optical Cable Corporation, assignee of this application, when an electrical signal of a given frequency is applied to a pair of conductors, unequal portions of signal energy is transmitted to the individual conductors of an adjacent pair by each conductor of the signal pair. The capacitive and inductive coupling between adjacent conductors are substantially higher than those couplings of the other conductors of the signal pair. The phenomenon of crosstalk is exaggerated when both conductors of the signal pair are placed adjacent to and outside of opposing conductors of the other signal pair. The extent of the crosstalk depends on the space between the adjacent conductors, the dielectric constant of the material between the adjacent conductors, and the distance in which such conductors are closely spaced and parallel to each other. Further, the extent of the crosstalk is a function of frequency, increasing logarithmically as the frequency of the signal increases.
There are some general design guidelines for reducing crosstalk, for example, placing the conductors after the signal transmission lines exit the modular jack so as to induce signals of opposite phase to those which were induced inside the plug or jack; routing a second signal pair in a pattern that is opposite in polarity to the pattern of the signal pair that produces crosstalk in the plug or jack. However, the addition or rerouting of the signal transmission lines causes impedance mismatch in the transmission system, thereby negatively affecting the structural return loss, voltage standing wave ratio, and combined system attenuation.
In light of the above, there exists a need for a transmission line design for reducing crosstalk without causing higher return loss.